1. Field of the Invention
The present invention concerns a method for removing a pressed board from the gap of a periodically operating press and for feeding a new board to be pressed to the gap of the press, whereby the removal of the pressed board and the feeding of the new board are performed during the same opening cycle. Periodically operating presses with one pressing gap are used for different pressing purposes of different boards, whereby in general also heating effect is exerted onto the board, besides the pressing effect. The heating effect can be implemented by means of heated pressure plates. One typical application of this kind is plating of boards with a film or the like. The board is in general a wood-containing board, like chipboard, batten-board or lattice-board, fiberboard or plywood. The invention also concerns an apparatus for implementing the method.
2. Description of Related Art
For the pressing purpose in question there is known a procedure, where the board to be pressed is fed, in a certain proceeding direction, into the immediate vicinity of the feeding side of the gap of the periodically operating press by means of a suitable conveyor, on which the board lies. On this area of readiness in the vicinity of the press, the board is gripped at its opposite side edges by gripping elements supported by feeding arms. The feeding arms form a first arm group, and they can be projected out to the grip distance from a vicinity of the guide bars supporting them. The guide bars extend continuously from the area of readiness past the opposite sides of the press, to the removing area of the pressed boards. Supported by the same guide bars there are also removing arms, the ends of which being equipped with gripping elements for gripping the pressed board in the opened gap of the press and for lifting it off from the lower pressure platen. The removing arms form the other arm group. After the removing arms have gripped to the board to be removed from the press, and respectively, after the feeding arms have gripped to the board to be pressed, the arms of the both groups are driven together in the removing, respectively in the feeding direction for a transfer path length, by which the pressed board can be removed from the press, and respectively, the board to be pressed can be fed into the open press gap. The feeding arms comprise elements for gripping the edge of the board by pressing. The removing arms, for their part, are equipped with elements for gripping to the surface of the board, primarily with suction pad elements. An apparatus using this procedure is disclosed, among others, in publication DE-A1-197 18 866.
EP-A1-0 908 282 discloses an apparatus, the operation of which follows the basic operations of the apparatus described above, that is, the board to be removed from the press is gripped at the upper surface, and the board to be fed to the press is gripped at the edges thereof by clamping. The gripping elements are supported by gripping arms, on which the gripping elements are movable in the transversal direction with respect to the transfer direction of the boards to be handled. Special for the construction described in this publication is that the movement of the groups of feeding arms and the groups of removing arms, respectively, in the transversal direction to the transfer direction of the boards can be implemented independently from each other. Prerequisite for achieving the described operations is, that the guides supporting the feeding and removing arms can be separated for achieving feeding and removing units, respectively, being movable in the direction perpendicular to the transfer direction of the board, independently from each other. It has been stated, that with the construction and the operation provided thereby, speeding up of the operating cycle can be achieved. The construction of the apparatus, however, does not provide moving of the boards in the operation direction of the apparatus so, that the feeding and removing movements of the boards could be staggered with respect to each other, which would be essential for speeding up the operation of the press.
This kind of staggering of the feeding and removing movements of boards is, on the other hand, possible with apparatus disclosed by U.S. Pat. No. A1 4,348,252 and U.S. Pat. No. A1 4,442,092.
In the above-mentioned disclosure, there is provided a feeding, removing carriage, to be driven into the opened gap of the press. The board to be pressed lies on top of a carriage to be driven into the gap, by which it is brought to the gap of the press, above the pressed board lying on the lower pressure plate. The lower side of the carriage is equipped with suitable surface gripping elements by which the pressed board can be gripped, when the carriage is driven to the gap, in order to lift it off from the lower pressure plate. After that the carriage is further driven out from the press, the pressed board hanging below the carriage. The board lying on top of the carriage and remaining to be pressed, for its part, is left supported only by edge supports, after the carriage has left the gap of the press. The board is lowered onto the lower pressure plate by drawing away the supports under the edges of the board. Prerequisite for the operation of the apparatus is, that the feeding and removing carriage performs a full-scale reciprocating movement in the transfer direction of the boards during the opening cycle of the press, which causes its own inevitable delay for the operation of the apparatus.
The removing and feeding device of a plate press, known from the above mentioned disclosure U.S. Pat. No. A1 4,424,092 is based on arms to be driven into the opened press gap from the side of the press, said arms supporting transfer and lifting means. The lifting means have been described as suction pad devices, for gripping to the pressed board, and by means of which it is lifted to the operation reach of suction transfer means supported by arms. With suction transfer device the board is then transferred away from the gap of the press. Supported by the arms there are provided also conveyor belts, on top of which the board to be pressed can be transferred to the gap of the press. The apparatus provides the removal movement of the pressed board independently from the feeding movement, and these movements can also be implemented staggered from each other. This makes it possible to speed up the operation of this device. One problem with this device is that both the feeding the removing devices are supported by the same arms, which is a constraint on performing the feeding and removing operations. One source of the problems is related to transporting the board set to the press in a loose state, supported on the conveyor belts. There is the risk that the laminating foil comes off during the quick feeding movement.